A class of machines exists in the art generally known as “scroll” machines for the displacement of various types of fluids. Such machines may be configured as an expander, a displacement engine, a pump, a compressor, etc., and the features of the present invention are applicable to any one of these machines. For purposes of illustration, however, the disclosed embodiments are in the form of a hermetic refrigerant compressor.
Generally speaking, a scroll machine comprises two spiral scroll wraps of similar configuration, each mounted on a separate end plate to define a scroll member. The two scroll members are interfitted together with one of the scroll wraps being rotationally displaced 180° from the other. The machine operates by orbiting one scroll member (the “orbiting scroll”) with respect to the other scroll member (the “fixed scroll” or “non-orbiting scroll”) to make moving line contacts between the flanks of the respective wraps, to define moving isolated crescent-shaped pockets of fluid. The spiral wraps are commonly formed as involutes of a circle, and ideally there is no relative rotation between the scroll members during operation; i.e., the motion is purely curvilinear translation (i.e., no rotation of any line in the body). The fluid pockets carry the fluid to be handled from a first zone in the scroll machine where a fluid inlet is provided, to a second zone in the machine where a fluid outlet is provided. The volume of a sealed pocket changes as it moves from the first zone to the second zone. At any one instant in time there will be at least one pair of sealed pockets; and where there are several pairs of sealed pockets at one time, each pair will have different volumes. In a compressor, the second zone is at a higher pressure than the first zone and is physically located centrally in the machine, the first zone being located at the outer periphery of the machine.
Two types of contacts define the fluid pockets formed between the scroll members, axially extending tangential line contacts between the spiral faces or flanks of the wraps caused by radial forces (“flank sealing”), and area contacts caused by axial forces between the plane edge surfaces (the “tips”) of each wrap and the opposite end plate (“tip sealing”). For high efficiency, good sealing must be achieved for both types of contacts; however, the present invention is primarily concerned with tip sealing.
The concept of a scroll-type machine has thus been known for some time and has been recognized as having distinct advantages. For example, scroll machines have high isentropic and volumetric efficiency, and, hence, are relatively small and lightweight for a given capacity. They are quieter and more vibration free than many machines because they do not use large reciprocating parts (e.g., pistons, connecting rods, etc.); and because all fluid flow is in one direction with simultaneous compression in plural opposed pockets, there are less pressure-created vibrations. Such machines also tend to have high reliability and durability because of the relatively few moving parts utilized and the relatively low velocity of movement between the scrolls. Scroll machines which have radial compliance to allow flank leakage have an inherent forgiveness to fluid contamination.
One of the difficult areas of design in a scroll-type machine concerns the technique used to achieve tip sealing under all operating conditions, and also during all speeds in a variable speed machine. Conventionally, this has been accomplished by (1) using extremely accurate and very expensive machining techniques, (2) providing the wrap tips with spiral tip seals, which, unfortunately, are hard to assemble and often unreliable, or (3) applying an axially restoring force by axial biasing the orbiting scroll or the non-orbiting scroll towards the opposing scroll using compressed working fluid. The latter technique has some advantages but also presents problems. Namely, in addition to providing a restoring force to balance the axial separating force, it is also necessary to balance the tipping moment on the scroll member due to pressure-generated radial forces which are dependent on suction and discharge pressures, as well as the inertial loads resulting from the orbital motion which is speed dependent. Thus, the axial balancing force must be relatively high, and will be optimal at only certain pressure and speed combinations.
The utilization of an axial restoring force requires one of the two scroll members to be mounted for axial movement with respect to the other scroll member. This can be accomplished by securing the non-orbiting scroll member to a main bearing housing by means of a plurality of bolts and a plurality of sleeve guides as disclosed in Assignee's U.S. Pat. No. 5,407,335, the disclosure of which is hereby incorporated herein by reference. In the mounting system which utilizes bolts and sleeve guides, arms formed on the non-orbiting scroll member are made to react against and slidingly engage the sleeve guides. The sleeve guides hold the scroll member in proper alignment. The non-orbiting scroll member experiences gas forces in the axial, radial and tangential direction whose centroid of application is at or near the mid-height of the scroll vane or wrap. The non-orbiting scroll member also experiences tip and base friction which can be randomly more on one than the other, but can be assumed as being equal and, therefore, having a centroid at or near the mid-height of the scroll wrap or vane. The non-orbiting scroll member additionally experiences flank contact forces from the centripetal acceleration of the orbiting scroll member which acts closer to the vane tip than at the base of the vane. All of these forces combine to yield a centroid of action which is located at a point just off the mid-height of the scroll wrap or vane toward the vane tip.
On scroll machines that incorporate axial compliance of one of the scroll members, it is necessary to provide a stop to limit the axial movement of the axial compliant scroll member.
When the orbiting scroll member is the axial compliant member, the orbiting scroll member will be biased against the non-orbiting scroll member during compressor operation and the orbiting scroll member will be limited in its axial movement away from the non-orbiting scroll member by a main bearing housing or by a fixed component of the scroll machine.
When the non-orbiting scroll member is the axial compliant member, the non-orbiting scroll member is typically mounted for axial movement on a set of sleeve guides. The non-orbiting scroll member is biased against the orbiting scroll member during compressor operation and the non-orbiting scroll member will move axially away from the orbiting scroll member by sliding along the sleeve guides. Typically, the sleeve guides are mounted to a main bearing housing or a fixed component of the scroll machine by a bolt with the head of the bolt acting as a stop to limit the axial movement of the non-orbiting scroll.
While utilizing the bolt head as a stop has performed satisfactory in most of the prior art designs of scroll machines. Newer scroll machines are being designed which require tighter control over the amount of axial travel provided. The combination of using a bolt with a sleeve guide and all of the tolerance stack-ups associated with this design do not permit the tighter control over the amount of axial travel without adding additional costs for the manufacture of the scroll machine.
The present invention provides the art with a sleeve guide which is designed to work in conjunction with another component of the scroll machine to accurately control the axial movement of the non-orbiting scroll member. The sleeve guide preferably works in conjunction with the partition to accurately control the amount of axial movement as well as provide a positive stop for the non-orbiting scroll member since the partition is secured to the shell of the compressor.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.